What is ocean sound?

Ocean sound refers to the collection of acoustic energy present in marine environments, encompassing a variety of sources, including sounds from marine animals, geophysical noise from waves, wind, rain, and human generated noise from shipping, sonar, and offshore construction. This collection of sound at a given place and time is often called a soundscape. Monitoring ocean soundscapes provides key insight to understanding ecosystem dynamics, detecting environmental changes, and managing the impacts of noise pollution on marine organisms. Learn more about ocean sounds at Discovery of Sound in the Sea.

Why do we care? Ocean sound is critical for the survival of many marine animals because it is a primary means of communication, orientation and navigation, finding food, avoiding predators, and choosing mates. As such, human activities that produce underwater sounds have the potential to negatively impact animals by reducing their ability to hear prey, predators, and each other. US National marine sanctuaries are home to many acoustically active marine animals and understanding the presence and impacts of noise is a conservation priority. Further, the occurrence and types of sounds present offer key insights on animal presence, species behaviors, human-use patterns, and changing ocean conditions.

When, where, & why are we listening?

NOAA’s Office of National Marine Sanctuaries (ONMS) maintains a nationally coordinated underwater sound monitoring network across the National Marine Sanctuary System, known as ONMS Sound. ONMS sound works with partners to monitor off the US East Coast, in the Gulf of Mexico, off the West Coast and in the Pacific Islands region. Ocean Sound monitoring sites are located in strategic locations within sanctuary boundaries and records continuously. Audio recordings and standardized sound measurements are available through the NOAA National Centers for Environmental Information’s Passive Acoustic Archive. Explore the acoustic monitoring sites here.

The Stellwagen Bank National Marine Sanctuary is a wild ocean place near an urban world, sits east of Boston, Massachusetts between Cape Ann and Cape Cod. Historically important as a fishing ground, New England’s only national marine sanctuary now reigns as a premier whale watching destination and continues to support commercial and recreational fishing.

Ocean sound monitoring within SBNMS has a long history of underwater acoustic monitoring with a focus on monitoring of marine mammal, including the endangered North Atlantic Right Whale presence. As well as noise reduction during vessel speed reduction programs.

Current ocean sound monitoring and analysis is maintained at four sites within SBNMS. Two sites (SB01, SB02,SB03) are located more inshore, capturing more local vessel activity and sounds from nearshore species. The one offshore sites (NRS09) capture patterns in migrating whales and transiting commercial vessel traffic and is part of the US Ocean Noise Reference Station Network.

Summary of ocean sound monitoring sites

Site Primary.monitoring.purpose Oceanographic.Setting Depth Seasonality Vessel.Traffic.Setting Latitude Longitude TotalDays StartDate Information
SB01 To monitor a site that supports seasonally high abundances of Atlantic cod and is located near a region of elevated commercial vessel activity. Continental shelf (<200m) 50 m Seasonal winds and baleen whales presence near inbound TSS lane to Boston, within existing Off Race Point SMA slowing large traffic in March-April 42.43855 -70.5458 852 2018-11-12 https://sanctsound.portal.axds.co/#sanctsound/sanctuary/monterey-bay/site/SB01
SB02 Part of Sanctuanry Soundscape Monitoring Project (2018-2022) Continental shelf (<200m) 68.3 m Seasonal winds and baleen whales presence NA 42.47000 -70.2300 NA 2018-11-12 https://sanctsound.portal.axds.co/#sanctsound/sanctuary/monterey-bay/site/SB02
SB03 To monitor shallow sandy habitat situated on the bank that supports the foraging and social activities of marine mammals. Continental shelf (<200m) 45 m Seasonal winds and baleen whales presence near outbound lane to Boston and within Off Race Point SMA slowing large traffic April-May; illegal scalloping in March-April 42.25557 -70.1788 1708 2018-11-12 https://sanctsound.portal.axds.co/#sanctsound/sanctuary/monterey-bay/site/SB03
NRS09 To continue long-history of monitoring trends in ocean noise, including cetacean species presense and vessel movement Continental shelf (<200m) 79 m Seasonal winds and baleen whales presence fan of traffic moving north to Canadian ports, but more distant/dispersed 42.40000 -70.1300 2701 2014-10-21 https://www.pmel.noaa.gov/acoustics/noaanps-ocean-noise-reference-station-network

What is a soundscape?

Soundscapes are complex – representing all the types of sounds present at a given time and location and influenced by the weather. How do we visualize this information? To orient you to the different contributions to a soundscape, in the figure below the colored lines represent seasonal differences, vertical lines indicate different sound sources of interest and what frequency(s) represents the source, and the black lines bound the soundscape to expected range at this location, when only wind noise is present. We can track these different features over time to understand how soundscape components are changing, and compare conditions across sites.

A visualization of ocean sound in nearshore habitat. Seasonal summary of measured sound levels (colored lines) shown as median hourly values over all available data. Vertical lines indicate representative frequencies for different sound sources: ship noise (63, 125 Hz), fin whales (20 Hz), blue whales (45 Hz), and humpback whales (500 Hz). The bottom bar shows how the data are distributed in the different wind categories: low < 5 m/s, med 5-10 m/s, high >10 m/s. Dotted lines are modeled wind noise at this depth based on Hildebrand et al 2021.A visualization of ocean sound in nearshore habitat. Seasonal summary of measured sound levels (colored lines) shown as median hourly values over all available data. Vertical lines indicate representative frequencies for different sound sources: ship noise (63, 125 Hz), fin whales (20 Hz), blue whales (45 Hz), and humpback whales (500 Hz). The bottom bar shows how the data are distributed in the different wind categories: low < 5 m/s, med 5-10 m/s, high >10 m/s. Dotted lines are modeled wind noise at this depth based on Hildebrand et al 2021.

The median power spectral densities (PSD) for all hours across all years are calculated from calibrated audio data using community software tools: Triton Soundscape Metrics, MANTA, or PyPAM. Triton software calculates the one-third octave band sound pressure levels by integration of PSD levels with a 1 Hz/1 second resolution and a median was used to calculate hourly values over no less than 1,800 1-s values for that hour and converted to decibels (dB re 1 μPa). MANTA and PYPAM software calculates power spectral density (PSD) levels per minute (μPa²) within the hybrid milledecade frequency bands. PAMscapes was used to calculate the median for each hour within one-third octave bands. These values were then converted to 1-Hz resolution to match the wind model results by converting to pressure and dividing by the band width before converting back to sound spectrum levels in decibels (dB re 1 μPa/Hz).

No one soundscape is alike and we can use other sites in similar oceanographic settings (e.g. nearshore or offshore) to compare conditions. From 2018-2022, the U.S. National Oceanic and Atmospheric Administration (NOAA) and the U.S. Navy engaged in a multi-year effort to monitor underwater sound within the U.S. National Marine Sanctuary System, known as Sanctuary SoundScape Monitoring Project. Data collected during this dedicated period provide initial insights on how soundscapes compare.

A visualization of ocean sound compared across other ONMS nearshore sites. Ocean sound data and analysis are part of the Sanctuary Soundcape Monitoring Project and summarized in publication on Advance the interpretation of shallow water marine soundscapesA visualization of ocean sound compared across other ONMS nearshore sites. Ocean sound data and analysis are part of the Sanctuary Soundcape Monitoring Project and summarized in publication on Advance the interpretation of shallow water marine soundscapes

What are the latest conditions in ocean sound?

Soundscapes are dynamic, changing with season and annual differences in sources (wind, biologics, and human-activity). Efforts to reduce noise are underway on global to local scales though vessel speed reduction strategies and engineering solutions. Measuring annual trends in ocean noise provide insights on trends in ocean noise: Are levels lower in the most recent year of monitoring?

Annual difference in Ocean SoundAnnual difference in Ocean Sound

How often is ship noise above threshold?

In many nearshore marine environments, vessels are transiting the region for a variety of reasons and adding noise to the soundscape. Using 100 Hz as an indicator of vessel noise, we measured how often vessel noise is above sound levels at the known wind conditions. This method helps to control for the influence of wind on a soundscape. Specifically, when wind is high, vessel noise exceedance will be lower, compared to lower wind speed conditions.

Noise ExceedanceNoise Exceedance

How much noise do nearby ships contribute to the soundscape?

vessels are transiting nearby. Vessels are considered nearby if transiting within 10 km of the monitoring location. When vessels are nearby sound levels increase. Vessel presence is tracked using Automatic Identification System (AIS) data that most vessel are required to transmit Noise ExceedanceNoise Exceedance

Difference in soundscape when ships nearby. Calculated as monthly average from daily differences in 125 Hz sound levels when vessel nearby verse no vessel nearby

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What are we learning?

Coming soon…